Projection system

ABSTRACT

A method for presenting secondary information to a video-viewing audience comprises projecting video images onto a screen and projecting invisible light signals encoded to represent secondary information associated with said video images onto the screen concurrently with said video images.

BACKGROUND

Projection systems for displaying motion pictures, television, videogames, digital video discs (DVDs), VCR tapes, digital cable, and thelike (collectively, “video”) generally include various electroniccomponents that receive, process, and selectively channel light from oneor more light sources (such as a light bulb) along one or morecorresponding optical paths to a projection lens. The projection lensprojects the channeled light onto a screen to form visible images, whichcan be viewed by human observers. Various versions of such systems arecommonly used in movie theaters, corporations, and residential homes forallowing people to view motion pictures, television, video games, andpresentations.

Projection systems also commonly include an audio source that transmitsaudio information relating to the projected images (a “soundtrack”) tospeakers, which are typically hard-wired to the audio source. Thespeakers may be integral with or physically-separated from theprojection system. The human observers can then hear the soundtrack asthey view the video.

Many times, there are multiple soundtracks associated with a givenvideo. For example, many DVDs include a standard soundtrack for themotion picture and a “director's narration” soundtrack, wherein thedirector of the motion picture narrates commentary over the standardsoundtrack. Further, for example, many DVDs include soundtracks inmultiple languages for the same video. Currently, when several peoplesimultaneously watch the same video in the same room, they areconstrained to listen to the same soundtrack. The inventors haverecognized that it would be desirable to have a projection system thatallows different human observers watching the same video to listen todifferent associated soundtracks simultaneously. For example, when agroup of people watch a video at the same time, some people in the groupmay want to listen to the standard soundtrack, whereas others may wantto listen to the “director's narration” soundtrack (or a differentlanguage).

Furthermore, it is common for the audio portion of many projectionsystems to include some version of “surround sound”, wherein thesoundtrack is delivered from speakers located at different places aroundthe room. The speakers used in most surround sound systems arehard-wired to the audio source of the projection system. Many times itis difficult to hard-wire remote speakers to the audio source in aconvenient and aesthetically-pleasing way. Accordingly, the inventorshave recognized that it would be desirable to have a projection systemthat facilities convenient, effective wireless installation of surroundsound systems to be used with the projection system.

The disclosed invention was developed in view of these and otherproblems associated with video projection systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an audio-visual system, implemented according to oneembodiment of the invention.

FIG. 2A illustrates an embodiment of a projection device, showing onepossible location of an integral secondary signal transmitter.

FIG. 2B illustrates an embodiment of a projection device, showing asecond possible location of an integral secondary signal transmitter.

FIG. 2C illustrates an embodiment of a projection device, showing athird possible location of an integral secondary signal transmitter.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary embodiment of a projection systemimplemented in accordance with the present invention. The projectionsystem generally includes a projection device 10, a secondary signaltransmitter 12, a screen 14, and at least one receiver 16 a, b. Theprojection device 10 projects video onto the screen 14 for humanobservers to watch. The screen 14 can comprise a number of differenttypes of surfaces upon which video images can be projected, such asreflective screens and surfaces (as used with front projection systemsshown in FIG. 1) and transflective screens (as used with rear projectionsystems, not shown). The secondary signal transmitter 12 projects asecondary light signal onto the screen 14 that is not visible to nakedhuman eyes. Useful formats for the secondary signals include, forexample, infrared (IR) signals and ultraviolet (UV) light. The secondarysignal is encoded with secondary information associated with the video,such as, for example, audio information. The secondary light signal isreflected off of the screen 14 (or a second screen, not shown) to thereceiver(s) 16, where it is received and decoded. When the secondaryinformation is audio information, it is decoded into audibly-perceptiblesounds. When the projection system is a rear-projection system, thesecondary light signal is transmitted through the transflective screento the receivers in the viewing room.

FIG. 1 illustrates secondary signal transmitter 12 in a locationindependent from projection device 10, though, as illustrated in otherembodiments herein, secondary signal transmitter 12 may be located at avariety of positions inside of or attached to the outside of projectiondevice 10. Irrespective of its position relative to the projectiondevice 10, secondary signal transmitter 12 is positioned so as totransmit an invisible encoded light signal to the screen 14 (or to asecond screen, not shown). The secondary light signal is reflected fromthe screen 14 to receivers 16 a and 16 b located in the same room as theprojection device 10. The receivers 16 a and 16 b are configured toreceive the reflected invisible signals and decode those signals intoaudibly-perceptible sounds, i.e., the soundtrack of the video. In thecase of a rear-projection system (not shown), the receivers wouldreceive the secondary light signal transmitted through the transflectivescreen. In various implementations of the invention, a single receivercould be used, or multiple receivers, as shown in FIG. 1, could be usedsimultaneously. Possible receivers include headphones 16 a and wirelessspeakers 16 b, as well as other types of receivers, that incorporate areceiver device (not shown) and a decoding device (not shown) forreceiving the secondary light signal and decoding it into anaudibly-perceptible sound.

The secondary signal transmitter 12 may encode the invisible secondarylight signals to represent audio information (or other types ofsecondary information) using a variety of methods, including digital oranalog modulation. Similarly, receivers 16 may be configured to decodethe secondary light signal using a variety of methods, such as digitalor analog demodulation, provided that the decoding method match theencoding method used by the secondary signal transmitter 12.

Though not necessary to implement the invention, in certain embodiments,the secondary signal transmitter 12 may be configured to transmitmultiple channels of audio information via the invisible light signalseffectively simultaneously. Transmitting multiple channels of audioinformation may be useful for allowing each human viewer watching avideo in the same room to listen to different associated soundtracks, aswell as for implementing wireless stereo and surround sound audiodelivery systems. One such method of transmitting and receivingdifferent channels of audio information via the invisible signal is bypolarizing the secondary signal before it is transmitted to the screen14 such that each channel of audio information has a differentpolarization. For example, a first channel of audio information could betransmitted by secondary signal transmitter 12 having a verticalpolarization, and a second channel of audio information could betransmitted by secondary signal transmitter 12 having a horizontalpolarization. Another method would include using multiple secondarysignal transmitters 12, each being configured to transmit a differentchannel of invisible signals toward screen 14 using various methods ofencoding, such as digital or analog modulation, to separate thedifferent channels of audio information represented by the invisiblelight signals.

When the system is configured to transmit multiple channels of audioinformation toward the screen 14 (or other screen), then it is desirablethat the receivers 16 be configured to be able to receive and decode thedifferent reflected channels of light signals carrying audioinformation. Depending on the implementation of the invention, thedifferent receivers 16 (e.g., the different speakers 16 b and headphonesets 16 a) each may be permanently pre-configured to receive and decodea particular channel of audio information. Alternatively, the differentreceivers 16 may each be configured with a channel selector, dial, orother mechanism for selecting different ones of the available channelsof audio information to receive and decode. For example, each speaker 16b and/or pair of headphones 16 a could be equipped with a channelselector (not shown) that would allow a user to selectively configurethe speaker to receive and decode a particular channel of audioinformation. Moreover, where headphones 16 a are used in the system,each speaker in a given set of headphones (i.e., each “ear”) could beconfigured (either permanently or selectively using a channel selector)to receive and decode different channels of the reflected audioinformation, which could be used to deliver stereo sound to the humanuser.

The transmission and reflection of different channels of audioinformation via the invisible light signals can be used in a variety ofways. For example, it is common for surround sound systems to deliverfive, seven, or more different channels of audio information, eachchannel being specific to a different speaker in the room. Therefore,where an embodiment of the invention is used to implement a surroundsound system in a room, each channel of audio information (via theinvisible secondary light signals) could be received and decoded by adifferent speaker 16 b in the room to effectuate the surround soundeffect. Moreover, where headphones 16 a are used as the receiver, each“ear” of the set of headphones could be permanently or selectivelyconfigured to receive a different channel of audio information todeliver a stereo sound to the listener. Further, the different channelsof transmitted audio information could be used to deliver differentsoundtracks associated with the same video to the different humanviewers in the same room. For instance, the secondary signal transmitter12 could be configured to transmit one or more channels of encoded audioinformation that represents a version of the associated soundtrack inEnglish, Spanish, and French, as well as a “director's narration”soundtrack, all effectively simultaneously. The human viewers could eachuse different receivers (e.g., headphone sets) to selectively determinewhich channel(s) of audio information to receive and decode. In thisway, different human viewers watching a video in the same room couldlisten to different soundtracks associated with the video.

The secondary signal transmitter 12 may take a variety of forms and belocated at a variety of positions within the system. The secondarysignal transmitter 12 may be positioned inside or outside of theprojection device 10, and, if outside, the secondary transmitter 12 maybe integral with, attached to, or physically-separate from (as shown inFIG. 1) the projection device 10. In one embodiment, the secondarytransmitter 12 is a light emitting diode (LED) that is configured toemit an infrared (IR) light signal. Of course, various other devices,including lasers, may be used as the secondary signal transmitter 12 totransmit invisible light signal toward screen 14. If the secondarysignal transmitter 12 is located separate from the projection device 10,then the secondary transmitter 12 may also include a separate lens (notshown) that projects the light signal emitted from the LED into thescreen 14 to maximize coverage of the screen 14. Though not necessaryfor the invention hereof, maximizing the surface area of the screen ontowhich the secondary signal is transmitted maximizes the efficiency andperformance of the reflected signal.

FIGS. 2 a-2 c illustrate an exemplary projection system 10 in schematicformat that could be used in connection with an embodiment of thepresent invention, as well as different possible implementations of thesecondary signal transmitter 12 integrated into the projection system10. This particular illustrated projection system 10 includes a lightsource 20, such as a bulb. The light source 20 emits light through acolor wheel 22, which reflects off of a digital micromirror device (DMD)24, which is comprised of a plurality of very small,individually-tiltable micromirrors (not shown), each of which beingconfigured to correspond to a unique pixel on the screen 14. Each of themicromirrors on the DMD is tilted so as to direct light from the lightsource 20 either toward or away from the screen 14. When directed towardthe screen 14, the light passes through a lens 26, which projects thelight onto the screen 14. By rapidly tilting each of the micromirrors soas to alternatively direct light toward and away from the screen 14 atdifferent frequencies, viewable images are projected through the lens 26onto the screen 14.

If the secondary signal transmitter 12 is positioned inside ofprojection device 10, it could be located at a variety of differentpositions therein. Though not necessary, it is useful to position thesecondary signal transmitter 12 such that it emits its invisible lightsignal through lens 26, which projects the signal onto screen 14. Inthis way, a single lens 26 can be used to display the visible lightimage of the video, as well as project the invisible light signalcarrying the audio information. The secondary signal transmitter 12 maybe positioned in a variety of ways to achieve this result. For example,as shown in FIG. 2 a, the secondary signal transmitter 12 could bemounted inside of the projection device 10 essentially in the path ofthe primary video light signal such that the secondary audio lightsignal is reflected by the DMD 24 through the lens 26 to the screen 14.Alternatively, the secondary signal transmitter 12 may be positioned, asshown in FIG. 2 b, such that the secondary signal is reflected by theDMD 24 through the lens 26, but so that it is done outside of theprimary light path from light source 20. In the embodiment shown in FIG.2 b, the secondary signal transmitter is positioned so that thesecondary light signal is reflected by each of the micromirrors on theDMD 24 when the micromirror is tilted “away” from the primary lightsource, and “toward” the secondary signal transmitter 12. In any givenvideo transmission, each micromirror is tilted “away” from the primarylight source a sufficient amount of the time to adequately reflect thesecondary light signal in this configuration. Finally, the secondarysignal transmitter 12 may be positioned “off-axis” relative to the lightpath reflected from the DMD 24, such that the secondary signaltransmitter 12 emits the invisible light signal directly through thelens 26 without being reflected by the DMD 24.

Embodiments of the invention provide various benefits. One such benefitis that viewers of the same video in the same room can listen todifferent soundtracks, depending on their preferences. This benefit isbest achieved where the receivers 16 are headphone sets 16 a. Further,where the system is used to implement a surround sound system, thespeakers used to implement the system can communicate with the audiosource wirelessly. Reflecting the secondary signal off of the screen 14provides a greater likelihood that the receivers 16 will receive thesecondary signal, as there is a greater likelihood that there will be aclear path between the screen 14 and the receivers 16 than between theprojection device 10 and the receivers 16. Other benefits of variousembodiments of the invention will be recognized by one skilled in theart.

While the present invention has been particularly shown and describedwith reference to the foregoing preferred and alternative embodiments,it should be understood by those skilled in the art that variousalternatives to the embodiments of the invention described herein may beemployed in practicing the invention without departing from the spiritand scope of the invention as defined in the following claims. It isintended that the following claims define the scope of the invention andthat the method and apparatus within the scope of these claims and theirequivalents be covered thereby. This description of the invention shouldbe understood to include all novel and non-obvious combinations ofelements described herein, and claims may be presented in this or alater application to any novel and non-obvious combination of theseelements. The foregoing embodiments are illustrative, and no singlefeature or element is essential to all possible combinations that may beclaimed in this or a later application. Where the claims recite “a” or“a first” element of the equivalent thereof, such claims should beunderstood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements. Further, theuse of the words “first”, “second”, and the like do not alone imply anytemporal order to the elements identified. The invention is limited onlyby the following claims

1. A projection system, comprising: a projection device configured toproject visible video images onto a screen; a secondary signaltransmitter configured to project invisible light signals onto saidscreen; and wherein said invisible light signals are encoded torepresent secondary information associated with said video.
 2. Thesystem of claim 1, wherein said secondary information is audioinformation.
 3. The system of claim 1, further comprising one or morereceivers configured to receive said invisible light signals projectedonto said screen and to decode said invisible light signals.
 4. Thesystem of claim 1, wherein said receivers comprise personal headphonesets configured to receive and decode said invisible light signals intoaudibly-perceptible sounds.
 5. The system of claim 1, wherein saidreceivers are loudspeakers configured to receive and decode saidinvisible light signals into audibly-perceptible sounds.
 6. The systemof claim 1, wherein said screen is a reflective surface.
 7. The systemof claim 1, wherein said screen is a transflective surface.
 8. Thesystem of claim 1, wherein said secondary signal transmitter isconfigured to project a plurality of channels of invisible light signalsonto said screen.
 9. The system of claim 8, further comprising one ormore receivers configured to receive said invisible light signalsprojected onto said screen and to decode said invisible light signalsinto audibly-perceptible sounds; and wherein said receivers are equippedto be selectively configured by a user to decode one of said pluralityof channels of invisible light signals into audibly-perceptible soundsat a given time.
 10. The system of claim 8, wherein said plurality ofchannels of invisible light signals represents alternative soundtracksassociated with said video images projected onto said screen.
 11. Thesystem of claim 8, wherein said plurality of channels of invisible lightsignals represents different channels of a single soundtrack having asurround sound feature.
 12. The system of claim 8, wherein saidplurality of channels of invisible light signals comprise polarizedlight signals.
 13. The system of claim 8, wherein said plurality ofchannels of invisible light signals comprise modulated light signals.14. The system of claim 1, wherein said invisible light signal comprisesinfrared light.
 15. The system of claim 1, wherein said invisible lightsignal comprises ultraviolet light.
 16. The system of claim 1, whereinsaid secondary signal transmitter comprises a light emitting diode. 17.The system of claim 1, wherein said secondary signal transmitter ispositioned outside of said video projection device.
 18. The system ofclaim 1, wherein said video projection device includes a lens throughwhich said video images are projected, and wherein said secondary signaltransmitter is positioned inside of said video projection device and isconfigured to emit said invisible light signal through said lens. 19.The system of claim 1, wherein said video projection device includes adigital micromirror device having a plurality of micromirrors that eachselectively reflects light from a primary light source through a lens;and wherein said secondary signal transmitter is positioned inside ofsaid video projection device and is configured to emit said invisiblelight signal such that it is reflected by a plurality of saidmicromirrors concurrently with light from said primary light sourcethrough said lens.
 20. The system of claim 1, wherein said videoprojection device includes a digital micromirror device having aplurality of micromirrors that each selectively reflects light from aprimary light source through a lens; and wherein said secondary signaltransmitter is positioned inside of said video projection device and isconfigured to emit said invisible light signal such that it is reflectedby each of said micromirrors through said lens at times when light fromsaid primary light source is not reflected through said lens by saidrespective micromirror.
 21. A method for presenting audio information toa video-viewing audience, comprising: projecting video images onto ascreen; and projecting invisible light signals encoded to representsecondary information associated with said video images onto said screenconcurrently with said video images.
 22. The method of claim 21, whereinsaid secondary information is audio information.
 23. The method of claim21, wherein said video images and said invisible light signals areprojected concurrently through a common lens.
 24. The method of claim21, wherein said invisible light signals comprise a plurality ofseparate channels of invisible light signals.
 25. The method of claim24, wherein said separate channels of invisible light signals aremodulated.
 26. The method of claim 24, wherein said separate channels ofinvisible light signals represent different soundtracks associated witha single video.
 27. The method of claim 24, wherein said separatechannels of invisible light signals represent different channels ofsurround sound audio information associated with a single soundtrack.28. The method of claim 21, further comprising the step of selectivelypolarizing said invisible light signals.
 29. The method of claim 21,further comprising receiving said reflected invisible light signals anddecoding said reflected invisible light signals into audibly-perceptiblesounds.
 30. A method for watching and listening to an audio-visualpresentation, comprising: viewing visually-perceptible light imagesprojected from a video projection device, which are projected onto ascreen; and listening to an audibly-perceptible soundtrack decoded frominvisible light signals projected onto said screen.
 31. The method ofclaim 30, wherein different persons viewing the same set ofvisually-perceptible light images listen to different soundtracksassociated with said set of projected light images.
 32. The method ofclaim 30, wherein said listening step includes listening to a pluralityof channels of audio information delivered from a plurality of speakers.33. An audio visual projection system, comprising: a means forprojecting video images onto a screen; and a means for projectinginvisible light signals onto said screen, said invisible light signalsbeing encoded to represent secondary information associated with saidvideo images.
 34. The system of claim 33, further including at least onereceiver configured to receive said invisible light signals projectedonto said screen and to decode said invisible light signals intoaudibly-perceptible sounds.
 35. A projection system, comprising: aprojection device configured to project visible video images onto afirst screen; a secondary signal transmitter configured to projectinvisible light signals encoded to represent secondary informationassociated with said video images onto a second screen; and wherein saidvisible video images and said invisible light signals are transmittedthrough a common lens concurrently.